<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<input type="text">
<script>
    let search = document.querySelector('input');
    document.addEventListener('keyup',function (e) {
       if (e.keyCode === 83) {
           search.focus();
       }
    });
</script>
</body>
</html>